I just did this on my 1991 W150. I decided to NOT drop the tank because right before the pump went south, I filled the damn tank! Soo, I did the truck bed tilt way. Worked out very easy and was a breeze. Those connectors are easy to get off safely if you are careful if you have room. And you have plenty if you tilt the bed. If you want me to walk you thru the tilt bed how too, let me know here and I'll do it happily. But generally, there is a clip in the connector that is or used to be white plastic, it is probably yellowed by now. When you have the bed u-p and out of the way before you do anything else pinch the clip with a tiny slim needle nose plyer and just pull the hose straight off.
Don't force anything and you'll get it.
to tilt the bed simple remove the two bolts in the front of the bed, and the two center ones, halfway loosten the back two and then hook up a engine hoist to the fornt of the bed and simply tilt it up outta the way for safety use a couple jackstands under the bed between it and the rails and you'll have all the room you need. Here's a video on a 1996 but it is the same proceedure. Don't worry about the pressure deal he explains because the tbi trucks have low pressure.
https://www.youtube.com/watch?v=XZSPFxthp0k